4 egg yolks
1/8 teaspoon grated nutmeg
¾ cup unsalted butter
¾ cup all-purpose flour
4 cups milk
Salt and pepper
¼ cup plus 1 tablespoon extra-virgin Greek olive oil
1 large onion, finely chopped
1 medium fennel bulb, finely chopped
2 garlic cloves, minced
1 teaspoon paprika
1 cup dry white wine
2-1/2 cups peeled, seeded, and chopped plum tomatoes, with their juice
2-1/2 pounds medium fresh shrimp, shelled, deveined, and finely chopped
Two 1-inch strips orange peel
2 tablespoons tomato paste
Pinch of sugar
11 ounces long tubular pasta, such as bucatini
Make the béchamel. In a medium bowl, whisk together the egg yolks and nutmeg and set aside. In a large pot over medium heat, melt the butter. When the foam begins to subside, stir in flour and cook, stirring, for about 1 minute. Pour in the milk slowly, whisking constantly. Continue whisking until the mixture thickens. Remove from the heat. Pour about ½ cup of the hot béchamel into the eggs, whisking vigorously, and pour the egg mixture into the béchamel, whisking. Season with salt and pepper. Cover with a kitchen towel and set aside.
Preheat the oven to 350 degrees. Heat the ¼ cup oil in a large, wide pot over medium heat, and sauté the onion and fennel until soft, about 10 minutes. Add the garlic and stir for 1 minute. Stir in the paprika. Add the wine, bring to a boil, and add the tomatoes, shrimp, and orange peel. Cover and bring to a boil over medium heat. Simmer for about 20 minutes, until the sauce is thick. Five minutes before removing from the heat, add the tomato paste and sugar. Remove the sauce from the heat, remove the orange peel, and stir in 1 cup of the béchamel.
While the sauce is cooking, bring a large pot of salted water to a rolling boil and add the pasta. Boil until a little firmer than al dente. Remove from the heat, drain in a colander, and return the pasta to the pot. Toss with the remaining 1 tablespoon of olive oil.
Assemble the pastitsio. In a lightly oiled 11 x 15 inch baking dish, spread out half of the pasta. Spoon half the shrimp sauce on top. Layer the remaining pasta and the remaining shrimp sauce over it and spread the béchamel on top. Bake, uncovered, for about 45 minutes, or until browned and bubbly. Cool slightly and serve.